The present invention relates to internal combustion engines, and, more particularly, to a variable flow venturi assembly for use in an exhaust gas recirculation system of an internal combustion engine.
An exhaust gas recirculation (EGR) system is used for controlling the generation of undesirable pollutant gases and particulate matter in the operation of internal combustion engines. Such systems have proven particularly useful in internal combustion engines used in motor vehicles such as passenger cars, light duty trucks, and other on-road motor equipment. EGR systems primarily recirculate the exhaust gas by-products into the intake air supply of the internal combustion engine. The exhaust gas which is reintroduced to the engine cylinder reduces the concentration of oxygen therein, which in turn lowers the maximum combustion temperature within the cylinder and slows the chemical reaction of the combustion process, decreasing the formation of nitrous oxides (NoX). Furthermore, the exhaust gases typically contain unburned hydrocarbons which are burned on reintroduction into the engine cylinder, which further reduces the emission of exhaust gas by-products which would be emitted as undesirable pollutants from the internal combustion engine.
When utilizing EGR in a turbocharged diesel engine, the exhaust gas to be recirculated is preferably removed upstream of the exhaust gas driven turbine associated with the turbocharger. In many EGR applications, the exhaust gas is diverted directly from the exhaust manifold. Likewise, the recirculated exhaust gas is preferably reintroduced to the intake air stream downstream of the compressor and air-to-air after cooler (ATAAC). Reintroducing the exhaust gas downstream of the compressor and ATAAC is preferred due to the reliability and maintainability concerns that arise if the exhaust gas passes through the compressor and ATAAC. An example of such an EGR system is disclosed in U.S. Pat. No. 5,802,846 (Bailey), which is assigned to the assignee of the present invention.
With conventional EGR systems as described above, the charged and cooled combustion air which is transported from the ATAAC is at a relatively high pressure as a result of the charging from the turbocharger. Since the exhaust gas is also typically inducted into the combustion air flow downstream of the ATAAC, conventional EGR systems are configured to allow the lower pressure exhaust gas to mix with the higher pressure combustion air. Such EGR systems may include a venturi section which induces the flow of exhaust gas into the flow of combustion air passing therethrough. An efficient venturi section is designed to Apump@ exhaust gas from a lower pressure exhaust manifold to a higher pressure intake manifold. However, because varying EGR rates are required throughout the engine speed and load range, a variable orifice venturi may be preferred. Such a variable orifice venturi is physically difficult and complex to design and manufacture. Accordingly, venturi systems including a fixed orifice venturi and a combustion air bypass circuit are conventionally favored. The bypass circuit consists of piping and a butterfly valve in the EGR flow path. The butterfly valve is controllably actuated using an electronic controller which senses various parameters associated with operation of the engine. The controllable actuator associated with the butterfly valve for controlling the EGR flow rate typically is connected with the butterfly valve through appropriate mechanical linkages, etc. Although such systems may provide effective EGR, they may be relatively complicated, difficult and expensive to manufacture, and may require replacement more often.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, a variable flow venturi assembly for use in an exhaust gas recirculation system of an internal combustion engine having a housing with an inner chamber, a combustion air inlet in communication with the inner chamber, and an exhaust gas inlet in communication with the inner chamber. A venturi valve is slidably disposed within the chamber. A venturi valve has a longitudinally extending throughhole with an inlet opening in communication with the combustion air inlet, an outlet opening and a venturi section interposed and in communication with each of the inlet opening and the outlet opening. The venturi valve further has at least one bypass port and at least one induction port. Each bypass port is in communication with a combustion air inlet and a throughhole. Each induction port is in communication with the exhaust gas inlet and the throughhole. An actuator slidably moves the venturi valve within the inner chamber of the housing.
In another aspect of the invention, an internal combustion engine having an intake manifold and a variable flow venturi assembly. The variable flow venturi assembly has a housing, a venturi valve and an actuator. The housing is attached to the intake manifold, and has an inner chamber, a combustion air inlet in communication with the inner chamber, and an exhaust gas inlet in communication with the inner chamber. The venturi valve is slidably disposed within the inner chamber. The venturi valve has a longitudinally extending throughhole with an inlet opening in communication with the combustion air inlet, an outlet opening and a venturi section interposed and in communication with each of the inlet opening an the outlet opening. The venturi valve further has at least one bypass port and at least one induction port. Each bypass port is in communication with the combustion air inlet and the throughhole. Each induction port is in communication with the exhaust gas inlet and the throughhole. An actuator slidably moves the venturi valve within the chamber of the housing.
In yet another aspect of the invention, a method of operating a variable flow venturi assembly in an exhaust gas recirculation system of an internal combustion engine has the steps of: providing a housing having an inner chamber, a combustion air inlet in communication with the inner chamber, and an exhaust gas inlet in communication with the inner chamber; providing a venturi valve slidably disposed within the inner chamber, the venturi valve has a longitudinally extending throughhole with an inlet opening in communication with the combustion air inlet, an outlet opening and a venturi section interposed and in communication with each of the inlet opening and the outlet opening, the venturi valve further has at least one bypass port and at least one induction port, each bypass port in communication with the combustion air inlet and the throughhole, each induction port in communication with the exhaust gas inlet and the throughhole; moving the venturi valve in a slidable manner within the inner chamber of the housing using an actuator; and covering each bypass port a selected amount dependent upon the moving step.